The undefeated Hohensalzburg Fortress is the defining feature of Salzburg's skyline, towering high above the Old Town on its lofty perch atop the Mönchsberg. Originally constructed in 1077 by Archbishop Gebhard, the castle was expanded over the years, taking its current form in the year 1500 under the guidance of Archbishop Leonhard von Keutschach. Built to monumental proportions, the castle is one of Europe's largest Medieval structures, its sprawling embrace a cornucopia of Medieval artistic and architectural riches. The State Rooms and Princely Chambers are the most lavishly adorned, closely followed by the Chapel of Archbishop Leonhard von Keutschach. Today, the castle houses the Museum of the Rainer Regiment, the Fortress Museum and the Marionette Museum, and hosts the annual Salzburg Fortress Concerts amid the mount's ancient trees. Multimedia displays and interactive experiences bring the Medieval Era alive at the Hohensalzburg Fortress, historic Salzburg's crowning glory.